1. Field of the Invention
This invention relates to an adjustable-length bicycle stem. At one of its ends, the stem carries the handlebar of the bicycle, and at its opposite end, it is attached to the upper portion of the pivoting tube that is mounted to rotate in the steering socket of the bicycle frame.
2. Description of the Related Art
The advantage of the adjustable length of the stem resides in the fact that it can be adapted to be convenient to individuals assuming a different position on the bicycle.
So as to implement an adjustment of the length of the stem to prevent, to a certain extent, producing a range of stems of different lengths, U.S. Pat. No. 5,842,385 also proposes housing the handlebar in an insert with an eccentric hole. However, the adjustment is relatively complicated to carry out since by rotating the insert, the angle of inclination of the stem is also modified.
This also applies to the adjustable-length stem that is described in the publication EP1759976 that uses an insert that consists of a cylindrical body in which an eccentric through hole is provided to accommodate the handlebar of the bicycle. The cylindrical body is in two parts that are connected to one another by rib and groove means to clamp the handlebar. This insert is placed in a cylindrical through hole of the stem that is closed toward the front by a U-shaped cap. The drawback of this implementation is that the height of the stem at this location is necessarily relatively significant to allow a meaningful movement of the stem in the horizontal and vertical directions, which corresponds to twice the eccentricity of the receiving hole of the handlebar. The stem that is obtained is consequently relatively bulky in its front part.
The document U.S. Pat. No. 5,404,769 describes an adjustable-length stem that operates according to the same principle as that of EP1759976, and the space requirement of the device emerges still more clearly from this document.
One of the purposes of this invention is thus to propose an adjustable-length stem that at its front end has the same height as for the remainder of the stem, which improves the appearance of the stem and makes it possible to reduce its weight.
So as to be able to adjust the tilt of the stem, the means for attaching the stem to the pivoting tube comprise articulation means as is known from, for example, the publications CN200992282, U.S. Pat. Nos. 5,327,798 or 5,842,385.
Furthermore, the selection of the height of the conventional stems is made by cutting the pivoting tube to the desired length, and annular inserts are then placed between the stem and the steering tube. This height is thus adjustable by varying the number of inserts.
In short, all of the known stems of this type are relatively complicated by their design and comprise a large number of parts to be assembled, which brings about heavy weight and high cost and often also a loss of rigidity of the unit.